Strange problem...please help!

[Bibill]

I have a problem and I hope I can have some advise from you.

 

1. When I let go of my gas at around 70 - 80 km/h (at my 4th gear), my car would vibrate a few times and then stop. Sometimes it is ok, sometimes it is not.

 

2. Also after my recent servicing, my mechanic helps me to tune my idling speed. Initially, my idling speed will drop once the aircon is switched on (to around 800). Now, my idling speed will increase when the aircon is switched on (from 800 to 1000 rpm). My mechanic says this should be a proper behaviour of a car. Is this true?

 

I have a gut feel that problem 1 is linked to problem 2. I am driving a Mazda 121.

 

Please help! Thanks a million!

[S2P2]

Hi Bibill.....

 

Eh....Welcome to MCF. Dunno if anyone has or not but i am sure i have not welcomed you.

 

What your mech say is right. the RPM should increase when aircon is on.

 

as for point 1, i have never heard a car dying off at 4th gear, only on first. any others can help comment on this?

[Bibill]

Hi CYQUEK,

 

Oh yes you have...8)...thanks...

 

Oh I forget to type in one more word....it vibrates and then stop vibrating. My car did not died at 4th gear. And my mechanic says that the "carpitor" is at fault. I don't know whether this is the right spelling as I heard him talking about it to me. Do anyone know what is it?

 

Thanks a million!

[Pauly75ts]

"it vibrates and then stop vibrating"

 

Hi! there, BiBill,

 

WELCOME!! to MCF. Enjoy yourself here, so that you can enjoy your car more.

 

Do you know if your car has a carburettor or fuel-injection?

 

Can I assume that the vibration happens everyday? Day & night? Even after you are driving the car the first time you start in the morning?

 

Do you have an RPM counter to monitor engine speed? Have you check your spark plugs?

 

Rgds

 

Paul Yong

[Bibill]

Hi Paul,

 

Oh yes, I have been enjoying this forum ever since I was here the first time. Everyday I read without fail. Really help me to become quite a car fan!

 

My car is fuel injection. Yes, vibration happens anytime of the day at around 70km/h, 4th gear. When I look at my RPM monitor, it is about 2000rpm. I have just changed my spark plugs on Saturday when I did my servicing.

 

Thank you so much for the response!

[Pauly75ts]

"I look at my RPM monitor, it is about 2000rpm"

 

Hi! there, BiBill,

 

Check to see if it will happen at 2,000rpm in every gear. If it does, it should be an ECU problem.

 

Rgds

 

Paul Yong

[GDIzen]

Welcome to MCF. I think CYQUEK is right as when aircon kicks in, the fast idle setting should increase yr rpm not decrease it. Maybe check yr fuel filter?